Planetary gear system arrangement with auxiliary oil system

ABSTRACT

A method of designing a gas turbine engine includes configuring a speed reduction device for driving a fan and configuring a lubrication system for lubricating components across a rotation gap. The lubrication system includes a lubricant input. A stationary first bearing receives lubricant from the lubricant input and has a first race in which lubricant flows. A second bearing for rotation is within the first bearing. The second bearing has a first opening in registration with the first race such that lubricant may flow from the first race through the first opening into a first conduit. The first bearing is configured to also include a second race into which lubricant flows. The second bearing has a second opening in registration with the second race such that lubricant may flow from the second race through the second opening into a second conduit. The first and second conduits deliver lubricant to distinct locations.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of United States Ser. No. 14/474,869,filed Sep. 2, 2014 which is now U.S. Pat. No. 9,677,420 granted Jun. 13,2017, which is a divisional of United States Ser. No. 14/266,888, filedMay 1, 2014, which is now U.S. Pat. No. 8,931,285 granted Jan. 13, 2015,which is a continuation of United States Ser. No. 13/428,491, filed Mar.23, 2012, which is a continuation-in-part application of United StatesSer. No. 12/902,525, filed Oct. 12, 2010, which is now U.S. Pat. No.8,813,469 granted Aug. 26, 2014.

FIELD

This invention relates to planetary gear trains and more particularly toa lubricating system for a planetary gear train.

BACKGROUND

Planetary gear trains are complex mechanisms that reduce, oroccasionally increase, the rotational speed between two rotating shaftsor rotors. The compactness of planetary gear trains makes them appealingfor use in aircraft engines where space is at a premium.

The forces and torque transferred through a planetary gear train placestresses on the gear train components that may make them susceptible tobreakage and wear. In practice, conditions may be less than ideal andplace additional stresses on the gear components. For example thelongitudinal axes of a planetary gear train's sun gear, planet carrier,and ring gear are ideally coaxial with the longitudinal axis of anexternal shaft that rotates the sun gear. Such perfect coaxialalignment, however, is rare due to numerous factors including imbalancesin rotating hardware, manufacturing imperfections, and transient flexureof shafts and support frames due to aircraft maneuvers. The resultingparallel and angular misalignments impose moments and forces on the gearteeth, the bearings which support the planet gears in their carrier, andthe carrier itself. These imposed forces and moments may cause gearcomponent wear and increase a likelihood that a component may break inservice. Component breakage is undesirable in any application, butparticularly so in an aircraft engine. Moreover, component wearnecessitates inspections and part replacements which may render theengine and aircraft uneconomical to operate.

The risk of component breakage may be reduced by making the gear traincomponents larger and therefore stronger. Increased size may also reducewear by distributing the transmitted forces over correspondingly largersurfaces. However increased size offsets the compactness that makesplanetary gear trains appealing for use in aircraft engines, and thecorresponding weight increase is similarly undesirable. The use of highstrength materials and wear resistant coatings can also be beneficial,but escalates the cost of the gear train and therefore does not diminishthe desire to reduce wear.

Stresses due to misalignments can also be reduced by the use of flexiblecouplings to connect the gear train to external devices such as rotatingshafts or non-rotating supports. For example, a flexible couplingconnecting a sun gear to a drive shaft flexes so that the sun gearremains near its ideal orientation with respect to the mating planetgears even though the axis of the shaft is oblique or displaced withrespect to a perfectly aligned orientation. Many prior art couplings,however, contain multiple parts that require lubrication and arethemselves susceptible to wear. Prior art couplings may also lackadequate rigidity and strength, with respect to torsion about alongitudinal axis, to be useful in high torque applications.

SUMMARY

In one exemplary embodiment, a method of designing a gas turbine engineincludes configuring a speed reduction device for driving a fan andconfiguring a lubrication system for lubricating components across arotation gap. The lubrication system includes a lubricant input. Astationary first bearing receives lubricant from the lubricant input andhas a first race in which lubricant flows. A second bearing for rotationis within the first bearing. The second bearing has a first opening inregistration with the first race such that lubricant may flow from thefirst race through the first opening into a first conduit. The firstbearing is configured to also include a second race into which lubricantflows. The second bearing has a second opening in registration with thesecond race such that lubricant may flow from the second race throughthe second opening into a second conduit. The first and second conduitsdeliver lubricant to distinct locations.

In a further embodiment of the above, the first bearing and the secondbearing are centered about a common axis and the first conduit isparallel to the axis and the first opening is perpendicular to the axis.

In a further embodiment of any of the above, the speed reduction deviceincludes a rotating carrier for supporting at least one planetary gear.The second bearing extends from the rotating carrier about an axis.

In a further embodiment of any of the above, the first conduit isparallel to the axis. The first opening is perpendicular to the axis.The first conduit lubricates the planetary gears.

In a further embodiment of any of the above, a first spray bar isdisposed on the carrier.

In a further embodiment of any of the above, the speed reduction deviceincludes an epicyclic gear train that has a sun gear. A plurality ofplanetary gears is configured to rotate about the sun gear. A stationaryring gear and a carrier are attached to the fan.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of the disclosed examples willbecome apparent to those skilled in the art from the following detaileddescription. The drawings that accompany the detailed description can bebriefly described as follows.

FIG. 1 is a schematic view, partially in section, of a gas turbineengine.

FIG. 2 is a sectional view taken along the lines 2-2 in FIG. 1.

FIG. 2A is a sectional view through the gear drive.

FIG. 3 is a sectional view taken along the lines 3-3.

FIG. 3A is a sectional view taken along the line A-A of FIG. 3.

FIG. 3B is a sectional view taken along the line B-B of FIG. 3.

FIG. 3C is a sectional view taken along the line C-C FIG. 3.

FIG. 4 is a sectional view of a portion of oil flow path A.

FIG. 5 is a sectional view of an upper portion of the planetary gearsystem of FIG. 1.

FIG. 6 is a sectional view of a lower portion of the planetary gearsystem of FIG. 1.

FIG. 7 is a sectional view of a flow of oil into gutters.

DETAILED DESCRIPTION

FIG. 1 shows a schematic cross-section of gas turbine engine 10. Gasturbine engine 10 includes low pressure spool 12, high pressure spool 14and fan drive gear system (“FDGS”) 16. Low pressure spool 12 includeslow pressure compressor 18 and low pressure turbine 20, which areconnected by low pressure shaft 22. High pressure spool 14 includes highpressure compressor 24 and high pressure turbine 26, which are connectedby high pressure shaft 28. Fan drive gear system 16 includes epicyclicgear train 30 that drives a fan assembly 32 by way of a carrier shaft34. Epicyclic gear train 30 includes sun gear 36, ring gear 38 andplanetary gears 40 as will be shown hereinbelow. A carrier 50 is shownschematically in FIG. 4 between shaft 34 and ring gear 38. Details ofthis connection are better shown in FIG. 2.

Low pressure spool 12 and high pressure spool 14 are covered by enginenacelle 42, and fan assembly 32 and nacelle 42 are covered by fannacelle 44. Low pressure spool 12, high pressure spool 14 and fanassembly 32 comprise a two-and-a-half spool gas turbine engine in whichepicyclic gear train 30 couples fan assembly 32 to low pressure spool 12with input shaft 46.

Fan assembly 32 generates bypass air for producing thrust that isdirected between engine nacelle 42 and fan nacelle 44, and core air thatis directed into engine nacelle 42 for sequential compression with lowpressure compressor 18 and high pressure compressor 24. Compressed coreair is routed to combustor 48 wherein it is mixed with fuel to sustain acombustion process. High energy gases generated in combustor 48 are usedto turn high pressure turbine 26 and low pressure turbine 20. Highpressure turbine 26 and low pressure turbine 20 rotate high pressureshaft 28 and low pressure shaft 22 to drive high pressure compressor 24and low pressure compressor 18, respectively. Low pressure shaft 22 alsodrives input shaft 46, which connects to epicyclic gear train 30 todrive fan assembly 32.

Referring now to FIG. 2 and FIG. 2A, a view of the planetary gear systemhaving exemplary oil supply system is shown. The system is comprised ofan input shaft 46, sun gear 36 attaching thereto a plurality ofplanetary gears 40 that rotate about the sun gear 36, stationary ringgear 38, and a carrier 50 that rotates about the star gear to drive thefan assembly 32. As the ring gear 38 is stationary, the rotation of thesun gear 36 causes each planetary gear 40 to counter-rotate relative tothe direction of rotation of the sun gear 36 and simultaneously to orbitthe sun gear 36 in the direction of the sun gear's rotation. In otherwords, whereas each planetary gear 40 individually counter-rotatesrelative to the sun gear 36, the group of planetary gears 40 co-rotateswith the sun gear 36. Moreover, as the carrier 50 is driven by therotation of the group of planetary gears 40, the carrier 50 alsoco-rotates with respect to the sun gear 36. Finally, as the fan 32 isdriven by the carrier 50 (via shaft 34), the fan 32 also co-rotates withrespect to the sun gear 36 and the low spool shaft 46. Thus, in thisembodiment, the fan 32 rotates in the same direction as the low pressurecompressor 18.

A first spray bar 41 is mounted to the carrier 50 in between eachplanetary gear 40 that lubricates the planet gears 40 and ring gear 38.A second spray bar 53 is attached to the first spray bar 41 and extendsforward to provide lubrication to the carrier shaft 34 that is supportedby tapered bearings 55 that are tensioned by spring 60.

The carrier 50 has a shaft 34 for driving the fan assembly 32, acircular body 65 for holding the planetary gears 40 and a cylinder 70projecting aft about the input shaft 46. The cylinder 70 also closelyinteracts with a stationary oil transfer bearing 75.

A grounding structure 80 holds the FDGS 16, the ring gear 38, forwardgutter 90 and aft gutter 95. The flexible coupling 85 is disposed aroundthe rotary input shaft 46. The forward gutter 90 and an aft gutter 95attach to and around the outer edge of the ring gear 38 to collect oilused by the system for reuse as will be discussed herein. Oil is inputthrough the stationary oil transfer bearing 75 to the cylinder 70 (e.g.also a bearing) as will be discussed herein.

Referring now to FIG. 3, a side, sectional view of the oil transferbearing 75 is shown. The oil transfer bearing 75 is prevented fromrotational movement by attachment of a link 100 via tab 110 to an oilinput coupling 105 that attaches to the stationary aft gutter 95 (seealso FIG. 2).

The oil transfer bearing 75 has a plurality of inputs to provide oil tothose portions of the FDGS 16 that require lubrication during operation.For instance, oil from tube 115 is intended to lubricate the taperedbearings 55, oil from tube 120 is intended to lubricate the planet gearbearings 125 (see FIG. 5), and oil from tube 130 is intended tolubricate the planet and ring gears, 38, 40. Though three inputs areshown herein, other numbers of oil inputs are contemplated herein.

Referring now to FIGS. 3A and 3B, the link 100 attaches via a pin 135 tothe ears 140 extending from the tab 110. The link 100 extends towards aboss 145 on the oil transfer bearing 75 and is attached thereto by aball 150 and a pin 155 extending through the ball and a pair of ears 159on the boss 145 on the oil transfer bearing 75. The ball 150 allows theoil transfer bearing 75 to flex with the rotary input shaft 46 astorqueing moments are experienced by the fan assembly 32 and otherportions of the engine 10. The link 100 prevents the oil transferbearing 75 from rotating while allowing it to flex.

Referring now to FIG. 3C, a cross-sectional view of the oil transferbearing 75 is shown. The oil transfer bearing has a first race 160 thathas a rectangular shape and extends around the interior surface 165 ofthe oil transfer bearing 75, a second race 170 that has a rectangularshape and extends around the interior surface 165 of the oil transferbearing 75 and a third race 175 that has a rectangular shape and extendsaround the interior surface 165 of the oil transfer bearing 75. In theembodiment shown, tube 120 inputs oil via conduit 181 into the firstrace 160.

Cylinder 70 which extends from the carrier circular body 65, has a firstoil conduit 180 extending axially therein and communicating with thefirst race 160 via opening 185, a second oil conduit 190 extendingaxially therein and communicating with the second race 170 via opening195 and a third oil conduit 200 extending axially therein andcommunicating with the third race 175 via opening 205. As the cylinder70 rotates within the oil transfer bearing 75, the openings 185, 195,205 are constantly in alignment with races 160, 170, 175 respectively sothat oil may flow across a rotating gap between the oil transfer bearing75 and the cylinder 65 through the openings 185, 195, 205 to theconduits 180, 190, 200 to provide lubrication to the areas necessary inengine 10. As will be discussed herein, oil from conduit 180 flowsthrough pathway A, oil from conduit 190 flows through pathway B and oilfrom conduit 200 flows through pathway C as will be shown herein.

Referring now to FIGS. 4 and 6, oil from the tube 115 flows into secondrace 170, through opening 195 into conduit 190. From conduit 190, theoil flows through path B into a pipe 210 in the first spray bar 41 tothe second spray bar 53 where it is dispersed through nozzles 215. Pipe210 is mounted into fixtures 220 in the circular body 65 by o-rings 225the oil FIG. 4, the journal oil bearing input passes through tube, andtube into transfers tubes through tube into the interior of eachplanetary gear. Each planetary gear has a pair of transverse tubescommunicating with the interior of the planetary journal bearing todistribute oil between the planetary gear and the ring gear and a set ofgears to provide lubricating area oil to the journal bearings 235themselves.

Referring now to FIGS. 3C and 5, the flow of oil through path A isshown. The oil leaves conduit 180 through tube 230 and flows aroundjournal bearings 235 that support the planet gear 40 and into theinterior of shaft 240. Oil then escapes from the shaft 240 throughopenings 245 to lubricate between the planetary gears 40 and the ringgear 38.

Referring to FIG. 6, the conduit 200 provides oil through pathway C intomanifold 250 in the first spray bar 41 which sprays oil through nozzles215 on the sun gear.

Referring now to FIG. 7, oil drips (see arrows) from the planetary gears40 and the sun gear 36 about the carrier 50 and is trapped by theforward gutter 90 and the aft gutter 95. Oil captured by the forwardgutter 90 is collected through scupper 265 for transport into anauxiliary oil tank 270. Similarly, oil captured by the aft gutter 95travels through opening 275 and opening 280 in the ring gear support 285into the forward gutter 90 to be similarly collected by the scupper 265to go to the auxiliary oil tank 270. Some oil passes through openings290, 295 within the ring gear 38 and drips upon the flexible coupling 85and migrates through holes 300 therein and drains to the main scavengearea (not shown) for the engine 10.

As is clear from FIGS. 5 and 7, there is a recess adjacent the outerperiphery of the ring gear 38. The recess identified by 602, can be seento be formed by half-recess portions in each of two separate gearportions 600 which form the ring gear 38. As is clear, the recess 602 isradially outwardly of the gear teeth 603 on the ring gear 38. Thisrecess helps balance force transmitted through the ring gear as thevarious interacting gear members shift orientation relative to eachother.

Referring now to the Figures, In view of these shortcomings a simple,reliable, unlubricated coupling system for connecting components of anepicyclic gear train 30 to external devices while accommodatingmisalignment therebetween is sought.

Although a combination of features is shown in the illustrated examples,not all of them need to be combined to realize the benefits of variousembodiments of this disclosure. In other words, a system designedaccording to an embodiment of this disclosure will not necessarilyinclude all of the features shown in any one of the Figures or all ofthe portions schematically shown in the Figures. Moreover, selectedfeatures of one example embodiment may be combined with selectedfeatures of other example embodiments.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

What is claimed is:
 1. A method of designing a gas turbine enginecomprising: configuring a speed reduction device for driving a fanassembly surrounded by an outer housing; configuring a lubricationsystem for lubricating components across a rotation gap, the lubricationsystem including a lubricant input, a stationary first bearing receivinglubricant from said lubricant input and having a first race ire whichlubricant flows, and a second bearing for rotation within said Firstbearing, said second bearing having a first opening in registration withsaid first race such that lubricant may flow from said first racethrough said first opening into a first conduit; and configuring saidfirst bearing to also include a second race into which lubricant flows,and said second bearing having a second opening in registration withsaid second race such that lubricant may flow from said second racethrough said second opening into a second conduit, with said first andsecond conduits delivering lubricant to distinct locations.
 2. Themethod of claim 1, wherein said first bearing and said second bearingare centered about a common axis and said first conduit is parallel tosaid axis and said first opening is perpendicular to said axis.
 3. Themethod of claim 2, wherein said speed reduction device includes arotating carrier for supporting at least one planetary gear and saidsecond bearing extends from said rotating carrier about said axis. 4.The method of claim 3, wherein said first conduit is parallel to saidaxis and said first opening is perpendicular to said axis and said firstconduit lubricates said planetary gears.
 5. The method of claim 3,further comprising a first spray bar disposed on said carrier.
 6. Themethod of claim 1, wherein said speed reduction device includes anepicyclic gear train having a sun gear, a plurality of planetary gearsconfigured to rotate about the sun gear, a stationary ring gear, and acarrier attached to said fan assembly.